When a pre tag is used in spoilers (as the 4-space code block doesn't work), the standard gray pre/code background is not hidden when the spoiler is, but the text color within is set to the spoiler block background. The result is that the text within is actually visible while the spoiler is hidden.

Hidden

See what I mean?

Text

Either the whole pre block should be hidden or the text within should be made the same color as its immediate (gray) background.

Observed on several different sites in Safari, Chrome, and Firefox on OSX Yosemite.

Also, apparently I should have asked it on the iOS app.
– KevinDec 15 '14 at 0:02

Also, any text within the spoiler, but after the <pre> tag is not rendered within a <p> tag (or any tag for that matter). This makes it difficult to hide on the mobile apps.
– Arie LitovskyDec 16 '14 at 16:08